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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9a3cd851e9ea2a636a7b8ed0f6e4a3d49d70d47ea9adb9de62818a5b2c74364d' 
  AND token = 'WYhWJFHNkNoHng7CC0+54kgPuR0t+AXbC0ygO2uqGUw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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