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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a42a8fdecaec35e2f4557ac58fd34611a326820582aad53d8cca1045e7cebc05' 
  AND token = 'AKXAaEMGTUPfL8UMyl2f+MM7GjQhWTbKzEQ7+dOoZ2c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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