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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a76aad9228a48d2a2b342a20f3891042d76cdf3a4f30a83d1f59eb2cd1ecf63a' 
  AND token = 'fhHlOnNEOQxp4eE4n+PkxI++RAm1UwjwZJpZA+PA+DU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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