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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a6f84c02e47c0fb8dde1a2e83a04e3434a8a2c9cee12500b8a598e5aa70b4cd' 
  AND token = '93hDpfa1M/Vw5w3BFuIlvKEtvrm0nhz+9oIaL9Ez9WQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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