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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '756bf3c44f4c3ddbd9d64ee8391d8ee5cc4264ee6e6ed6960af8fc6941b12e78' 
  AND token = 'bBH19+mxzGnBAS5upaeDecDrg8rdjOfyQaOcXMFjCBA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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