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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c875582fc3492fa742df1969c21393012463eef5aaa84e0d46f969f9b6ad1135' 
  AND token = '+Dinu4qtUjhSZN3cSuCYvY4W9RHzMqTURTkGdIN5m1I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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