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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f5cf22aa2a492d4e8d7410e75c61f68aa716b19d3b6b83b09f4b81d58e0b49cd' 
  AND token = 'PLyls6T1JEWfKxnIfQUnFIKo6U5gzO0JaYAnZKKgbI0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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