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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c21f3f7d6e91c2c2e523a9bdcbfdd60859e298138cd2c0359bb1475e3b75fcb3' 
  AND token = 'WksaKMiYoqZPMCTLk46Iq2Fd4z4SatwMSjzwSxGy9jY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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