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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c39ba63629987894a21086357975ddbca72a69d42129e9df4ae6b940bdcbe818' 
  AND token = 'sBCKQVHaXtTNe/Xu/8Pd9p1ipMPwd/jnFmjbjmcRrXs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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