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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a51e02e75873976ea643e1f7b00f6d7c1532d5725c6ecc8ac5fdfadf939522c2' 
  AND token = 'ay/Kvc0PwBN5Rn5uJ3S8RI8KMk4OKI8iEh1s/PyNN1g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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