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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '278590c0f6d4eef404e52ec0ca182b940ea5fbb3d62342e7e33a09f30ce4aca4' 
  AND token = 'Chw08iEtH7RqKpTWxcFvGP0AOgaQPIAdbkBXEWTmFiU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}