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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '255716154b2082b394f436463ca44cff3b2953d758118755345379162525b729' 
  AND token = '+QKLJFbnIHGgn5npK+TMzZ5C09ddS+Y635r2oaqPL74=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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