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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21bde37fdd5c3c586d00437390a2668538cdd1ef07f9cf967434a47029dcc144' 
  AND token = '4/YTLT9hUG+A+BBoahttoqrr2wavJsHI5+amIrvh4Es=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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