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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '387265aa3577d5b0d02539332270af1e6d8703575cdf85a110d21ccbf4a008b9' 
  AND token = 'dD441aMmsFkMda98XPQqEiko97+B7UW10RpzNU4/wX4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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