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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b15a1555bf3fa3fe7a79d12f2e6e7d0e9ca7015a42b9d2bb60dca5024b9bc18d' 
  AND token = '5YAzTDDUg/WAAR3aykHDHk9L1u+OchHKmfXd8OvI4aE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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