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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4a0f70d6fe0aa38918e9d8d6d10f0aa8d13476528db7439bee698c4c5fd97f4' 
  AND token = 'IIFtSNV2k+zNaoMnZIPkis1eYgejiDMX4yD1BQeB/0k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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