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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a03547d9ee5f2ec229b64f4d62d5822d0d3b82bbee37b3f6ff54d553b0aa1d8' 
  AND token = 'rF5JqcsyVhkrB+Qpuzt/WNITiu+iEUkcq6Dld40Qf7s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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