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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c5085d256e7f567f23b85330296b725ed619bc46586e6acf83947b0d3e0ab78a' 
  AND token = 'PMn1V20r+MupsDefqyxdTWIThs1evvn1SSBm282aEpA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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