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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '342b5bc62080fa4b71cbe2281f54a23cdcae792ccbc0ed4c9833fc1b07a63d5a' 
  AND token = 'Rt4EKUflsmHfZTxjGQxKG5RMi2Cpq3yeH+xRes1zXaU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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