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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '688ff49aa91befec9ebf036fc723114656eb38232e0b29a8b4a45590eeeeafcf' 
  AND token = 'nef9miE6jRD5ewJbCUM9nr4zKqUydHOS4JLDLn4bf20=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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