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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5c8b4a88db627e80cc08fa6e65f555f95e901da04048849428064ce87a6a5d1c' 
  AND token = '5+KPOvEHTbEOU/+TYToobFPJzEfEHpitik99Z26yMDE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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